Laser therapy, or preferably, Low reactive-Level Laser Therapy (LLLT) is now being recognized as a valid medical tool, with the theories advanced from clinical experiences and double-blind trials being backed up by research data. From its beginnings with Professor Endre Mester’s experiments and clinical trials at the end of the 1960's, LLLT has steadily increased in applications to include an increasing number of medical specialties. The historical background of LLLT is given. The author examines the physical basics of LLLT, and demonstrates the differences between photoactivative laser therapy and photodestructive laser surgery. The α-effect phenomenon of simultaneous LLLT which was reported by early workers in conventional high-powered laser surgery is examined, and the development of pure LLLT is discussed. Wavelength-dependency is discussed, and the importance of methodology is demonstrated. The author discusses the importance of the use of correct terminology in writing or discussing LLLT, and the necessity for accurate and consistent reporting of LLLT therapeutic parameters. Some possible pathways of LLLT are examined, Examples are given showing a wide range of practical multispecialty clinical applications of LLLT, gained from the successful diode laser and combined laser therapy of pure and combined LLLT in over 12 000 patients over the past 13 years. Simultaneous LLLT, concomitant with laser surgery, is not included in these figures.

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Hydroxyapatite (HAP) is a well-accepted biocompatible material used in the repair of bony defects of the oral cavity and jawbone. Low reactive-level laser therapy (LLLT) has been reported as accelerating the repair of bone fractures, and in controlling side-effects from the inflammatory reaction such as oedema. The present study examines the effects of hemilateral He-Ne laser irradiation (632.8 nm, 6 mW, 10 min, daily for 4 days) on HAP implants in bilateral artificially-created defects in the rabbit mandible. The contralateral unirradiated side served as control. At 21 days postimplantation macroscopically and microscopically the irradiated implants showed better bonding with the surrounding bone margins, and a greater degree of osteogenesis than the unirradiated implants, which tended to be loose, or to have totally dislodged. It was concluded that, with pathways and mechanisms as yet not fully understood, LLLT controlled the inflammatory response to the HAP implant resulting in better implant bonding and osteogenesis at the implant borders.

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Investigations on rats with an implanted tumour-carcinosarcoma of Walker (26 animals), cancer of the mammary glands, RMK-1 (75 animals) and in mice with spontaneous cancer of the mammary gland (188 animals)-have shown that the application of a low-level diode laser beam (890 nm) can effect the growth of the experimental tumour. Minimal doses produce a tumouro-static effect, while other doses produce different effects. Low level laser irradiation promotes dystrophic and necrotic changes in tumoural nodes.

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Non-linearity in photobiostimulation is described as a process where linear optical absorption produces active chemicals such as cytoplasmic H⁺ and Ca²⁺ which participate in chemical reactions whose reaction rates depend non-linearly on the concentration of these photoproduced active chemicals, thus allowing very sensitive light control of non-linear biological reactions. Important contributions to neural excitability and growth include photostimulation of ATP production which fuels the action potential and fills the synaptic ATP vesicles. As was recently shown, the synaptic ATP plays the important role of an extracellular neurotransmitter. The importance of this effect on the possibility of systemic laser therapy of nervous disoders by photostimulation of ATP release by migrating macrophages is mentioned. The connection between light-enhanced electrical activity of the nerve and neurite growth is also analysed.

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Low reactive-level laser therapy (LLLT) has been reported as effective in treating the intractable pain of chronic post herpetic neuralgia, but no reports have appeared on the use of LLLT on the acute phase of Herpes zoster. A case report is presented on a 37-year-old female who presented with an early stage atack of Herpes zoster. HeNe laser LLLT was applied in the scanning mode, in combination with epidural block therapy. The patient was taken off all forms of treatment after only 3 weeks, with no residual pain. The normal period is a minimum of 4 weeks, with some residual pain. The authors suggest that LLLT is a valid, easily applied and noninvasive adjunctive therapeutic technique to speed recovery from Herpes zoster attacks, especially when applied in the early stages of the attack.

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